This invention relates to an integrated circuit driver. More particularly, this invention relates to a pseudo-differential output driver.
Drivers are common circuits used for transmission of signals, either between integrated circuits (“ICs”) or within a single IC. For instance, driver circuitry can be used to transmit (1) data to and from a memory or (2) control signals to and from a memory controller. There are many types of drivers, each with their own advantages and disadvantages.
One type is a “single-ended” output driver, which receives an input signal and generates an output signal. Information is typically conveyed by the voltage of the output signal, which is substantially equal to either a relatively high voltage, such as that of a power supply (“VCC”), or a relatively low voltage, such as that of ground (“VSS”). Single-ended drivers are relatively simple, consume relatively little area, require a relatively low pin count, and have relatively low capacitance. However, they are quite susceptible to noise and jitter, such as that caused by unregulated power supply voltages.
In contrast, a “differential” output driver receives substantially concurrently two input signals and generates substantially concurrently two output signals. Information is typically conveyed by the voltage difference between the two output signals, with one voltage substantially equal to VCC and the other voltage substantially equal to VSS. Such pairs of input and output signals are known as differential signals. Differential output drivers are relatively immune to noise and jitter, because any noise or jitter that affects the voltage of one output signal will often affect in substantially the same way the voltage of the other output signal. However, differential drivers are often relatively complex, consume a relatively large amount of area, require a relatively high pin count, and have relatively high capacitance.
In view of the foregoing, it would be desirable to be able to provide a single-output driver with greater immunity to noise and jitter, while maintaining small size and low driver capacitance.